Originally only the spin-allowed transition energies were calculated.
Since then Horst Stratemeier generously provided info on how
the data points used to create the diagrams in the Ligand Field Theory
text by Figgis and Hitchman were generated. A set of runs was then done
using CAMMAG and a small script was written to manipulate the output data
into spreadsheets to give the Tanabe-Sugano diagrams
that now contain both spin-allowed and spin-forbidden lines.

Procedure for a Cr(III) system using the d3 diagram

Print the appropriate Tanabe-Sugano diagram and locate where
the ratio of the second to first peak matches that found
experimentally.

Tabulate the values of v1 / B, v2 / B, v3 / B from the
Y-intercepts and Δ/B from the
X-intercept.

A laboratory experiment based on this is described in more
detail in the
CHEM2110 lab manual. An interactive web page can be
used to do this more easily since a TS applet has been created
to display the d3 diagram and this is fed information from
the spectral display using JSpecView, Jmol and JavaScripts.

Created and maintained by Prof. Robert J.
Lancashire,
The Department of Chemistry, University of the West Indies,
Mona Campus, Kingston 7, Jamaica.Created Feb 1999. Links checked and/or last
modified 20th July 2016.
URL
http://wwwchem.uwimona.edu.jm/courses/Tanabe-Sugano/TSspread.html